To ensure a faultless passage of a nonwoven material or sliver through the nip line of a pair of rotating rollers, adhering fibers and impurities must constantly be cleared from the surface of the rollers. This also applies, in particular, to nipping rollers on carding machines or drawing frames, to which vegetable impurities contained to an increased extent in the nonwoven material and crushed by the rollers, as well as fibers, remain stuck.
For the cleaning of rollers with an essentially smooth surface, such as nipping rollers and drawing-frame rollers, it is known to use stationary stripping knives or strippers, the front edge of which is pressed against the roller surface (German Offenlegungsschrift No. 1,510,318 and German Patent Specification No. 1,166,669). However, during the cleaning of the rollers, impurities and fibers stripped from the roller settle on the front edge of the knife and have to be removed from time to time. It is important, above all, to ensure that fiber material jammed between the roller and the stripping knife is removed since these jammed fibers impair the cleaning effect of the stripping knife and, when accumulated in relatively large amounts, can render the stripping knife completely inoperative.
The disadvantage of manual elimination of the jammed fiber material, in which the stripping knife is lifted off from the roller, is that the roller remains uncleaned during this time, and consequently, a break in the nonwoven material can be caused. The machine then has to be stopped, thus resulting in a loss of production. A production loss also occurs when the machine is stopped from the outset for reasons of safety.
It has already been proposed, therefore, that the material deposited in front of and on the stripping knife be removed by means of a tab fastened to a rotating cylinder and be thrown in the direction of a suction element (German Offenlegungsschrift No. 1,510,318). In this case, as a result of the jerky movement of the tab, even fibers jammed between the stripping knife and the roller will be released or torn. Although this known device makes it possible to leave the stripping knife in its working position so that the cleaning of the roller is not interrupted, nevertheless, its cleaning effect is unsatisfactory in terms of the removal of jammed fibers, since predominantly only portions of these fibers are torn off and the remaining fiber residues remain jammed.
The object of the present invention is to remove reliably and in a simply way the fiber accumulations impairing the effectiveness of the stripping knife, without interrupting the cleaning of the roller, and thereby guarantee that the stripping knife remains operable.